Since Volume 1 of the Paint Booth Airbrushing series dealt with the basics of airbrush handling, it may seem odd to skip basic spraying techniques and jump right to strategies for diluting paint. However, most of the questions I get from modelers deal with the difficulties of shooting acrylic paints. So, let’s dive into some techniques for spraying two of the better-known acrylics, Vallejo and LifeColor. Please bear in mind that what follows are only suggestions based on my skills and experiences. There are as many good techniques for spraying acrylic paints as there are modelers spraying them. With that in I mind, please take whatever you find useful from the following suggestions, combine it with your own experience, and develop a technique that best suites you.
Vallejo Vs LifeColor:
I’ve used both of these brands for years and between the two, I prefer LifeColor. That said, Vallejo (meaning Vallejo Model Air and Vallejo Model Color) is both easier to shoot and easier to handle after its dry. In addition Vallejo paints come in handy dropper-cap bottles making measuring more accurate and easy. A quality bottle is perhaps why Vallejo paints also have a long shelf life. However, in my hands, LifeColor produces a smoother finish and dilutes out very nicely for fine-line work. Moreover, when compared to established standards (RLM color chips), LifeColor is surprisingly accurate. Color accuracy is a big consideration for me. On the down side, LifeColor has a marked tendency to dry on the needle. Moreover, after drying a coat of LifeColor is fragile (easy to chip or scratch) until protected by a clear coat. In contrast, Vallejo is less fragile when dry and likewise slightly less prone to dry on the needle—slightly.
Diluting Vallejo and LifeColor for Airbrushing:
The performance of Vallejo and LifeColor is greatly improved by the addition of a wetting or flow agent. My preferred flow enhancer is Liquitex Flow Aid. The addition of Liquitex to Vallejo and LifeColor drastically reduces needle build-up, decreases rough pebbly over-spray, and produces a more smooth, even finish. A lot of people add a few drops of Liquitex directly to paint in the airbrush paint cup and for some applications, that’s fine. I prefer to prepare a large volume of Vallejo or LifeColor thinner to which Liquitex has been added to 5%. These 5% stock solutions are what I use to dilute my paint. Having a premade mix of Thinner-Liquitex makes preparing paint mixtures easier and reproducible. Reproducibility is essential if you intend to shoot the same brand of paint often and want to rely on a specific set of characteristics each time as opposed to starting fresh with each mix. Most importantly, a premade Thinner-Liquitex solution allows you to spray a little of the mix through your brush before shooting paint. This helps prevent needle build up and makes clean up easier as well (see Airbrushing Vol. 1). Lastly, Thinner-Liquitex solutions have a long shelf life if properly stored so your mix will be ready when you need it.
Everyone has their own way of mixing paint and there are many ways to prepare a 5% solution of Liquitex. What follows are examples of multiple methods. Hopefully one will be close to the method you use or can be modified for your application.
Milliliters and Percent Volume:
I usually prepare 40ml of Thinner-Liquitex at a time. This requires 2ml (or 40 drops) of Liquitex to make a 5% solution. Brace yourself for the shameless plugs. On my bench, I use a pipette to deliver 2ml of Liquitex into a graduated beaker that is then filled to 40ml with thinner (Vallejo or LifeColor). After mixing, the solution is poured into a 40ml bottle, marked with a Sharpie, and stored for use.
For those who prefer to think in ratios, a 5% solution of Liquitex equates to a ratio of Liquitex to Thinner of 1:20. Apply whatever method of measurement you prefer and enjoy.
For the drop counters out there (I consider myself one), small batches of Thinner with 5% Liquitex are easily prepared by adding one drop of Liquitex to 20 drops of thinner. Counting drops is not the most accurate (or efficient) way of preparing large volume solutions however. In an effort to make it easier, the following chart provides the volumes of common airbrush paint cups and the amount of Liquitex (in drops or milliliters) that would have to be added to make a 5% solution.
Airbrush Paint Cup Liquitex Drops Liquitex Milliliters
2ml 2 0.1
5ml 5 0.25
10ml 10 0.5
In case you’re re-cycling old paint bottles, here’s a chart of common brands, their volumes, and the amount of Liquitex that should be added to a full bottle to achieve a 5% solution.
Brand (Vol. in ml) Liquitex Drops Liquitex Milliliters
Tamiya or Gunze (10) 10 0.50
Model Master (14.7~15) 15 0.750
Vallejo Paint (17) 17 0.85
LifeColor (22) 22 1.1
Alclad (29.5~30) 30 1.5
Vallejo Primer (200) 200 10
On the chance that you have some Model Paint Solutions storage bottles, here’s a chart showing the amount Liquitex that should be added to a full bottle to make a 5% solution.
MPS Bottle Liquitex Drops Liquitex Milliliters
6ml 6 0.30
10ml 10 0.50
20ml 20 1
40m 40 2
Adding the Paint—Finally:
For average airbrushing jobs, I dilute Vallejo Model Air (not Vallejo Model Color) and LifeColor to roughly ~30% or ~1/3 paint in the appropriate Thinner-Liquitex mix. Vallejo Model Color is much thicker than is Vallejo Model Air and requires diluting to ~10-15% paint. All of the dilutions provided in this article pertain to Vallejo Model Air. For some applications where I want better coverage, I might use 40% paint. However, a mix of ~30% paint is what I would use to shoot the blue of a Hellcat, the olive drab of a P-39, or the RLM-65 of a Bf-109 (apologies to the non-airplane people for all the aircraft references). A mix of ~30% paint is not ideal for fine-line shooting, however. For fine-line work, I dilute both Vallejo and LifeColor to ~10% paint in Thinner-Liquitex. (Note: Fine-line airbrushing techniques will be the focus of a future Paint Booth article.) In general, I err on the side of lean or less paint, especially if I’m going to be shooting on top off pre-shading. In this situation, I reduce the paint to ~20% in Thinner-Liquitex. A thinner paint mix will require more passes for good coverage. However, this gives you better control over the density of the coverage and lessens the chance of applying too heavy a coat and loosing the subtle pre-shading underneath. In the extreme, a thick coat of paint can also obliterate engraving and subtle details on the models surface. My working rule is: The thinner the layer of paint, the better.
Configuring the Airbrush:
Now that we’ve diluted the paint and we’re ready to shoot, let’s take a few moments and consider how the airbrush can be configured for general spraying. For general airbrush work (defined above) I use an Evolution or Infinity airbrush fitted with 0.2 or 0.4mm tip depending on the size model I’m spraying. By tip I’m referring to the combination of nozzle and needle. A 0.2mm tip is good for applying primary coats on small 1/72 scale aircraft (single seat). For larger 1/72, 1/48, and 1/32, I use a 0.4mm tip. A small tip (0.15mm) is best suited for fine-line work. In contrast, primers are best applied using a 0.4mm tip. Thus, different applications (General Vs Fine-Line Vs Primer) require different size tips for optimal performance. This is one of the primary reasons I use Harder & Steenbeck brushes. All three of the aforementioned tips (.15, .20, .40) are available for the Evolution, Infinity, and Grafo airbrushes. Most importantly, unlike other airbrushes, the novel socket design of the Harder and Steenbeck nozzle makes them self-centering; there are no fine threads or tiny wrenches to deal with. Simply unscrew the aircap and the nozzle literally drops out. The installation of a different size nozzle and needle takes 2-3 minutes allowing you to easily and quickly configure your brush for the job at hand.
With my brush fitted with a 0.4mm tip and filled with my 30% paint mix, I’m going to dial in ~12-15 psi on the ole’ air compressor dial. For general spraying 12-15 psi is a good place to start. For fine-line work, the ideal pressure is down around ~8-10 psi (more on this in a future article). Conversely, I usually spray clear coats and primers at a higher pressure of ~15 psi. As with most airbrushing techniques, experiment with different pressure settings until you find what works best for you.
Keeping the Needle Clean:
Although addition of Liquitex decreases paint build up on the needle, it does not prevent it all together. Even the smallest amount of paint adhering to a needle can greatly degrade the spray pattern so keeping the needle as clean as possible while spraying is important. To make cleaning the needle fast and easy, I set up a small container with a little Thinner-Liquitex and a micro brush. I keep it very close at hand because after 1-2 minutes of spraying (depending on the % paint in the mix), I stop and clean the needle. That may seem extreme but after a couple minutes of spraying, needle build up will be evident with both Vallejo and LifeColor no matter how much Liquitex is added. It’s the nature of the acrylic beast. To clean the needle, I carefully run the micro brush across the needle (read 90 degrees) never parallel to it. No pressure is exerted beyond simply moving the brush. If you remember to continuously clean the needle while spraying you’ll be rewarded with a better spray pattern, viewer blobs and splatters, and an overall smoother finish.
I hope you found something helpful there. Both Vallejo and LifeColor are great paints that perform nicely if tamed with a little Liquitex. With regards to other additives, Vallejo produces two reagents Thinner Medium (#73.524) and Airbrush Flow Improver (#71.62) that are described as wetting agents. I’ve not tried the Flow Improver but I have tested the Thinner Medium as a means of diluting Vallejo for fine-line work but that’s for a future article. For those who prefer Model Master acrylic paint, you can follow the same guidelines as for Vallejo and LifeColor: 5% Liquitex added to Model Master Acrylic Thinner (#50496) then paint diluted to ~30% by volume. I shot Model Master Acrylics for years with great results.
Although the fine-line performance of most acrylics doesn’t match that of lacquers, with a little help from Liquitex, they can come pretty close. For general airbrush work however, Vallejo and LifeColor acrylics are just as good as lacquer/enamels and they don’t stink the house up.
Now go paint something!